M. Kitao et al., Residual charges and infrared absorption in electrochromic WO3 films prepared by hydrogen-introduced sputtering, SOL EN MAT, 70(2), 2001, pp. 219-230
Electrochromic WO3 films were prepared by rf-sputtering in atmosphere consi
sting of Ar/H-2/O-2 mixed gas. The as-sputtered films require several times
of injection/extraction of ions (the aging) for obtaining reversible color
ation/bleaching. After the aging, there are ions (protons) remaining in the
films, namely residual charges. From the results of IR absorption of the a
s-sputtered and aged films, the residual charges contribute to create OH an
d HOH bonds. Hydrogen introduced in the films during sputtering is transfor
med only into OH bonds combining with unstable oxygen in the films. The int
roduced hydrogen is considered to suppress the growth of grain in WO3 films
from AFM observation. (C) 2001 Elsevier Science BN. All rights reserved.